How to Check Word DOCX Files for OLE Threats in Node.js

The OLE feature available in Word DOCX files makes it easy to integrate content from multiple applications into one central document. Unfortunately, it’s also easy for threat actors to exploit OLE technology by embedding malicious links or objects within a DOCX file.

If we make the mistake of opening DOCX files containing malicious OLE content, disaster can strike quickly. For example, a DOCX file containing executable code could initiate a malware download from a remote server.

Thankfully, using a free API, we can scan DOCX files to check them for OLE embedded objects. We can use the results of this scan to block OLE enabled files uploaded or shared from untrusted locations and thereby avert the risk of a sudden attack.

We can take advantage of this API using ready-to-run Node.js code examples to structure our API call.

To start, let’s install the client SDK. Let’s run the following command to install using NPM install:

npm install cloudmersive-virus-api-client --save

Alternatively, we can add the Node client to our package.json:

  "dependencies": {
    "cloudmersive-virus-api-client": "^1.1.9"
  }

Next, let’s quickly turn our attention to API call authorization. We’ll need a free Cloudmersive API key to authorize our requests (this will allow us to make up to 800 API calls per month with no commitments).

Finally, we can call the function using the below code. Our API response will contain a true or false “ContainsOleEmbeddedObject” value indicating if OLE was present within our file:

var CloudmersiveVirusApiClient = require('cloudmersive-virus-api-client');
var defaultClient = CloudmersiveVirusApiClient.ApiClient.instance;

// Configure API key authorization: Apikey
var Apikey = defaultClient.authentications['Apikey'];
Apikey.apiKey = 'YOUR API KEY';



var apiInstance = new CloudmersiveVirusApiClient.ScanApi();

var inputFile = Buffer.from(fs.readFileSync("C:\\temp\\inputfile").buffer); // File | Input file to perform the operation on.

var opts = { 
  'allowExecutables': true, // Boolean | Set to false to block executable files (program code) from being allowed in the input file.  Default is false (recommended).
  'allowInvalidFiles': true, // Boolean | Set to false to block invalid files, such as a PDF file that is not really a valid PDF file, or a Word Document that is not a valid Word Document.  Default is false (recommended).
  'allowScripts': true, // Boolean | Set to false to block script files, such as a PHP files, Python scripts, and other malicious content or security threats that can be embedded in the file.  Set to true to allow these file types.  Default is false (recommended).
  'allowPasswordProtectedFiles': true, // Boolean | Set to false to block password protected and encrypted files, such as encrypted zip and rar files, and other files that seek to circumvent scanning through passwords.  Set to true to allow these file types.  Default is false (recommended).
  'allowMacros': true, // Boolean | Set to false to block macros and other threats embedded in document files, such as Word, Excel and PowerPoint embedded Macros, and other files that contain embedded content threats.  Set to true to allow these file types.  Default is false (recommended).
  'allowXmlExternalEntities': true, // Boolean | Set to false to block XML External Entities and other threats embedded in XML files, and other files that contain embedded content threats.  Set to true to allow these file types.  Default is false (recommended).
  'allowInsecureDeserialization': true, // Boolean | Set to false to block Insecure Deserialization and other threats embedded in JSON and other object serialization files, and other files that contain embedded content threats.  Set to true to allow these file types.  Default is false (recommended).
  'allowHtml': true, // Boolean | Set to false to block HTML input in the top level file; HTML can contain XSS, scripts, local file accesses and other threats.  Set to true to allow these file types.  Default is false (recommended) [for API keys created prior to the release of this feature default is true for backward compatability].
  'restrictFileTypes': "restrictFileTypes_example" // String | Specify a restricted set of file formats to allow as clean as a comma-separated list of file formats, such as .pdf,.docx,.png would allow only PDF, PNG and Word document files.  All files must pass content verification against this list of file formats, if they do not, then the result will be returned as CleanResult=false.  Set restrictFileTypes parameter to null or empty string to disable; default is disabled.
};

var callback = function(error, data, response) {
  if (error) {
    console.error(error);
  } else {
    console.log('API called successfully. Returned data: ' + data);
  }
};
apiInstance.scanFileAdvanced(inputFile, opts, callback);

We can use the API response to take subsequent actions on our file and prevent it from reaching compromising locations.

The underlying service will also deep-verify our file format and perform signature-based and behavior-based virus and malware scans on the file contents.